A camera equipped with a zoom lens has been commercially available. In the zoom lens, a plurality of lens groups are moved in the direction of an optical axis to change a focal length of the zoom lens by changing spaces of the plural lens groups.
Further, there is known a camera wherein its optical axis is bent by 90° by arranging a prism in an optical system of a zoom lens. The camera of this kind has a merit that a lens barrel does not protrude in the course of photographing.
A zoom lens is composed of many single lenses and lens groups. Therefore, when the zoom lens is incorporated in a lens barrel, the property of the zoom lens is adversely affected by errors in respective lenses and by assembly errors.
Under the aforesaid background, there are provided patent publications about lens barrels. For example, Unexamined Japanese Patent Application Publication (JP-A) No. 2007-271648 discloses a lens barrel including a zoom lens whose optical system includes an adjusting lens for shift-adjustment in the direction perpendicular to an optical axis of the optical system for correcting errors in respective lenses and assembly errors.
In JP-A No. 2007-271648, the adjusting lens is fixed on a lens frame, and the lens frame is held on a housing together with other lenses to be shiftable in the direction perpendicular to the optical axis. This lens barrel is composed of two housings, and one housing holds a front optical system of a zoom lens, and the other housing holds a rear optical system of the zoom lens. Then, the lens frame that holds the adjusting lens is arranged at a position where the two housings are connected.
Unitizing a lens barrel by constituting it with two housings improves efficiency in terms of assembly and repairing, but it increases errors when securing lens property.
Therefore, it is considered to arrange the entire optical system of the zoom lens in one housing, which reduces errors compared with employing a lens barrel constituting with two housings. However, there still remain errors in respective lenses and assembly errors even when employing a single housing, because a zoom lens is composed of many lenses. It also requires an adjusting lens for a shift-adjustment.
In the lens barrel, an inside of the housing is formed variously in terms of shapes and dimensions depending on a lens to be held. The housing is generally molded with resin. Therefore, the housing is formed to have a cross section in a substantially square shape and to have one surface extending in parallel with the optical axis being open. A metal mold for forming the inside of the housing is drawn out in the direction that the housing opens. In other words, the housing is formed to have a cross section in a U-shape obtained when cutting the housing in the direction perpendicular to the optical axis, and a metal mold that forms the inside of the housing is drawn out in the direction of the opening of this U-shape.
However, when the metal mold for forming the inside of the housing is drawn out in this way, a draft angle in a certain degree is needed. A lens frame that holds an adjusting lens is held on a wall portion provided inside the housing extending in the direction that is almost perpendicular to the optical axis. Thus, the wall portion has a draft angle because the wall portion is formed by drawing out of the metal mold in the same way as described above.
As a result, the lens frame that holds the adjusting lens is tilted by the draft angle of the wall portion, resulting in a problem that the adjusting lens is also tilted away from the optical axis, which adversely affects lens property.
The housing may be molded without a draft angle on the wall portion. However, when deformation and shrinking is caused after molding in this case because of characteristics of resin, a surface of the wall portion that holds the adjusting lens would be tilted in the opposite direction to the tilt of the draft angle, in some cases. As a result, there is also caused a problem in a tilt of the adjusting lens in the same way as in the above description.
Further, even in the case where the housing is molded without a draft angle of the wall portion, and the wall portion does not tilt after being molded, the lens barrel would not provide sufficient lens property in some cases, due to a balance with a lens frame that holds other lenses. In this case, it is sometimes possible to obtain better lens property by tilting the adjusting lens intentionally.
In the meantime, when the lens barrel is formed by two housings and a lens frame that holds an adjusting lens is arranged at a position where the two housing are connected as shown in JP-A No. 2007-271648, the wall portion that is in contact with the lens frame can be formed by drawing the mold in the optical axis direction. Therefore, a draft angle is not needed and the aforesaid problem is not caused. Therefore, JP-A No. 2007-271648 discloses neither problems nor an embodiment about correction of the tilt of the adjusting lens.